Sterically hindered oxime color improvers for polyolefin processing

ABSTRACT

Sterically hindered oximes provide polyolefin compositions, including those also containing a phenolic antioxidant, with improved resistance to discoloration during processing at elevated temperatures.

The instant invention pertains to polyolefin compositions stabilizedagainst discoloration during processing by the presence of a stabilizingamount of a sterically hindered oxime.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 2,497,061 describes alkanedione dioximes as antioxidantsfor elastomers and drying oils. No mention is made of their use as colorimprovers for polyolefins during processing either alone or incombination with a phenolic antioxidant. The dioximes of U.S. Pat. No.2,497,061 are not sterically hindered and fall outside the scope of theinstant invention.

The synthesis of sterically hindered oximes is described in CanadianPatent No. 1,053,668. Their use as "spin-labels in molecules ofbiological interest, as inhibitors of vinyl polymerization, orinhibitors of hydrocarbon oxidation . . ." is suggested within the text.Their use as color improvers during polyolefin processing is notsuggested. The bis(sterically hindered oximes) of the present inventionare new compounds.

J. L. Brokenshire, et al., J. Amer. Chem. Soc., 94, 7040 (1972); G. D.Mendenhall, et al., J. Amer. Chem. Soc., 95, 2963 (1973); and CanadianPatent No. 1,053,668 all describe the preparation of stable iminoxyradicals from sterically hindered oximes.

European Patent Application 52,573 discloses the use of hydroxylaminesplus oximes to improve the color of phenolic antioxidants duringpreparation of said antioxidants. Diethylhydroxylamine and methyl ethylketomine are preferred components.

U.S. Pat. Nos. 4,566,901 and 4,576,628 disclose oxime ethers which areuseful for agricultural purposes as safeners. U.S. Pat. No. 4,028,412describes α-hydroxy (benzoin) oximes as chelating agents for copper. Theinstant sterically hindered oximes are structurally distinguished fromthe compounds described in these patents.

OBJECTS OF THE INVENTION

One object of the invention is to provide polyolefin compositionsstabilized against discoloration during processing by the presence of aneffective stabilizing amount of a sterically hindered oxime.

Another object of this invention is to provide new sterically hinderedoximes useful as process stabilizers for polyolefins.

DETAILED DISCLOSURE

The instant invention pertains to a polyolefin composition stabilizedagainst discoloration during processing which comprises

(a) a polyolefin, subject to discoloration during processing, and

(b) an effective stabilizing amount of a compound of the formula I##STR1## wherein R₁ is a tert-alkyl group of 4 to 18 carbon atoms, arylof 6 to 10 carbon atoms or said aryl substituted by one or two alkyl of1 to 4 carbon atoms or by one or two alkoxy of 1 to 4 carbon atoms,

R₂ and R₃ are independently alkyl of 1 to 18 carbon atoms, cycloalkyl of5 to 12 carbon atoms, phenylalkyl of 7 to 9 carbon atoms, aryl of 6 to10 carbon atoms, or said aryl or said phenylalkyl substituted on thephenyl ring by one or two alkyl of 1 to 4 carbon atoms or by one or twoalkoxy of 1 to 4 carbon atoms; or R₂ and R₃ together are a straight orbranched chain alkylene of 4 to 10 carbon atoms,

n is an integer from 1 to 4,

when n is 1, T is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12carbon atoms, phenylalkyl of 7 to 9 carbon atoms, aryl of 6 to 10 carbonatoms, or said aryl or said phenylalkyl substituted on the phenyl ringby one or two alkyl of 1 to 4 carbon atoms or by one or two alkoxy of 1to 4 carbon atoms,

when n is 2, T is alkylene of 2 to 12 carbon atoms, xylylene, arylene of6 to 10 carbon atoms or said arylene substituted by one or two alkyl of1 to 4 carbon atoms or by one or two alkoxy of 1 to 4 carbon atoms, and

when n is 3 or 4, T is alkanetriyl of 3 to 10 carbon atoms, oralkanetetrayl of 4 to 10 carbon atoms.

Preferably, R₁ is tert-alkyl of 4 to 8 carbon atoms, phenyl or phenylsubstituted by one or two alkyl of 1 to 2 carbon atoms or by one or twoalkoxy of 1 to 2 carbon atoms.

R₂ and R₃ are preferably independently alkyl of 1 to 8 carbon atoms.

Preferably, n is 1 or 2.

When n is 1, T is preferably alkyl of 8 to 18 carbon atoms or benzyl.

When n is 2, T is preferably alkylene of 2 to 10 carbon atoms.

Most preferably, R₁ is tert-butyl, phenyl or phenyl substituted by oneor two methyl or by one or two methoxy.

R₂ and R₃ are most preferably methyl.

When n is 1, T is most preferably alkyl of 12 to 18 carbon atoms,especially n-octadecyl.

When n is 2, T is most preferably alkylene of 4 to 8 carbon atoms,especially hexamethylene.

When R₁ is tert-alkyl, it is, for example, tert-butyl, tert-amyl,tert-octyl, tert-dodecyl or tert-tridecyl. When any of R₁, R₂, R₃ or Tis alkyl, it is, for example methyl, ethyl, isopropyl, n-butyl,sec-butyl, isobutyl, tert-butyl, tert-amyl, 2-ethylhexyl, n-octyl,tert-octyl, lauryl or n-octadecyl; when said radicals are cycloalkyl,they are, for example, cyclopentyl, cyclohexyl, cyclooctyl andcyclododecyl; when said radicals are phenylalkyl, they are, for example,benzyl, phenethyl, α-methylbenzyl and α,α-dimethylbenzyl; when saidradicals are aryl or substituted aryl, they are, for example, phenyl,naphthyl, tolyl, xylyl and 3,4-dimethoxyphenyl. When R₂ and R₃ togetheror T is alkylene, alkylene is, for example, ethylene, tetramethylene,hexamethylene, octamethylene, 2,2-dimethyl-1,3-trimethylene,dodecamethylene or 1,2-propylene; when said radicals are arylene, theyare, for example, phenylene, naphthylene or dimethylphenylene; when T isalkanetriyl or alkanetetrayl, T is, for example, glyceryl, thealkanetriyl radical derived from trimethylolethane or fromtrimethylolpropane, pentaerythrityl or 1,2,3,4-butanetetrayl.

The compounds of this invention are conveniently obtained by thepreparation of an appropriate tertiary nitrile intermediate followed byreaction of said nitrile with a tert-alkyllithium. The desiredsterically hindered oxime is isolated after treatment with ethanol,acetic acid and hydroxylamine hydrochloride following the method ofMendenhall, et al., J. Amer. Chem. Soc., 95, 2963 (1973). Theintermediates required to carry out the Mendenhall process are largelyitems of commerce or can be made by methods known in the art.

Substrates in which the compounds of this invention are particularlyuseful are the polyolefins, such as polyethylene and polypropylene.Polypropylene is particularly well stabilized by the instant compoundsduring processing.

While the instant compounds of formula I are quite effective processstabilizers for polyolefins when used alone, compositions which alsocontain a phenolic antioxidant are also extremely well stabilized duringprocessing by this combination of process stabilizers.

The compounds of formula I where n is 2 to 4 are new compounds notdisclosed or suggested by the prior art. Compounds where n is 2 areparticularly preferred.

In general polymers which can be stabilized include

1. Polymers of monoolefins and diolefins, for example polyethylene(which optionally can be crosslinked), polypropylene, polyisobutylene,polybutene-1, polymethylpentene-1, polyisoprene or polybutadiene, aswell as polymers of cycloolefins, for instance of cyclopentene ornorbornene.

2. Mixtures of the polymers mentioned under 1), for example mixtures ofpolypropylene with polyisobutylene.

3. Copolymers of monoolefins and diolefins with each other or with othervinyl monomers, such as, for example, ethylene/propylene,propylene/butene-1, propylene/isobutylene, ethylene/butene-1,propylene/butadiene, isobutylene/isoprene, ethylene/alkyl acrylates,ethylene/alkyl methacrylates, ethylene/vinyl acetate or ethylene/acrylicacid copolymers and their salts (ionomers) and terpolymers of ethylenewith propylene and a diene, such as hexadiene, dicyclopentadiene orethylidene-norbornene.

4. Polystyrene, poly-(p-methylstyrene).

5. Copolymers of styrene or methylstyrene with dienes or acrylicderivatives, such as, for example, styrene/butadiene,styrene/acrylonitrile, styrene/ethyl methacrylate,styrene/butadiene/ethyl acrylate, styrene/acrylonitrile/methyl acrylate;mixtures of high impact strength from styrene copolymers and anotherpolymer, such as, for example, from a polyacrylate, a diene polymer oran ethylene/propylene/diene terpolymer; and block polymers of styrene,such as, for example, styrene/butadiene/styrene,styrene/isoprene/styrene, styrene/ethylene/butylene/styrene orstyrene/ethylene/propylene/styrene.

6. Graft copolymers of styrene, such as, for example, styrene onpolybutadiene, styrene and acrylonitrile on polybutadiene, styrene andalkyl acrylates or methacrylates on polybutadiene, styrene andacrylonitrile on ethylene/propylene/diene terpolymers, styrene andacrylonitrile on polyacrylates or polymethacrylates, styrene andacrylonitrile on acrylate/butadiene copolymers, as well as mixturesthereof with the copolymers listed under 5), for instance the copolymermixtures known as ABS-, MBS-, ASA- or AES-polymers.

7. Halogen-containing polymers, such as polychloroprene, chlorinatedrubbers, chlorinated or sulfochlorinated polyethylene, epichlorohydrinhomo- and copolymers, polymers from halogen-containing vinyl compounds,as for example, polyvinylchloride, polyvinylidene chloride, polyvinylfluoride, polyvinylidene fluoride, as well as copolymers thereof, as forexample, vinyl chloride/vinylidene chloride, vinyl chloride/vinylacetate, vinylidene chloride/vinyl acetate copolymers, or vinylfluoride/vinyl ether copolymers.

8. Polymers which are derived from α,β-unsaturated acids and derivativesthereof, such as polyacrylates and polymethacrylates, polyacrylamide andpolyacrylonitrile.

9. Copolymers from the monomers mentioned under 8) with each other orwith other unsaturated monomers, such as, for instance,acrylonitrile/butadiene, acrylonitrile/alkyl acrylate,acrylonitrile/alkoxyalkyl acrylate or acrylonitrile/vinyl halogenidecopolymers or acrylonitrile/alkyl methacrylate/butadiene terpolymers.

10. Polymers which are derived from unsaturated alcohols and amines, oracyl derivatives thereof or acetals thereof, such as polyvinyl alcohol,polyvinyl acetate, polyvinyl stearate, polyvinyl benzoate, polyvinylmaleate, polyvinylbutyral, polyallyl phthalate or polyallyl-melamine.

11. Homopolymers and copolymers of cyclic ethers, such as polyalkyleneglycols, polyethylene oxide, polypropylene oxide or copolymers thereofwith bis-glycidyl ethers.

12. Polyacetals, such as polyoxymethylene and those polyoxymethyleneswhich contain ethylene oxide as comonomer.

13. Polyphenylene oxides and sulfides, and mixtures of polyphenyleneoxides with polystyrene.

14. Polyurethanes which are derived from polyethers, polyesters orpolybutadienes with terminal hydroxyl groups on the one side andaliphatic or aromatic polyisocyanates on the other side, as well asprecursors thereof (polyisocyanates, polyols or prepolymers).

15. Polyamides and copolyamides which are derived from diamines anddicarboxylic acids and/or from aminocarboxylic acids or thecorresponding lactams, such as polyamide 4, polyamide 6, polyamide 6/6,polyamide 6/10, polyamide 11, polyamide 12,poly-2,4,4-trimethylhexamethylene terephthalamide, poly-p-phenyleneterephthalamide or poly-m-phenylene isophthalamide, as well ascopolymers thereof with polyethers, such as for instance withpolyethylene glycol, polypropylene glycol or polytetramethylene glycols.

16. Polyureas, polyimides and polyamide-imides.

17. Polyesters which are derived from dicarboxylic acids and diolsand/or from hydroxycarboxylic acids or the corresponding lactones, suchas polyethylene terephthalate, polybutylene terephthalate,poly-1,4-dimethylol-cyclohexane terephthalate,poly-[2,2-(4-hydroxyphenyl)-propane] terephthalate andpolyhydroxybenzoates as well as block-copolyether-esters derived frompolyethers having hydroxyl end groups.

18. Polycarbonates.

19. Polysulfones, polyethersulfones and polyetherketones.

20. Crosslinked polymers which are derived from aldehydes on the onehand and phenols, ureas and melamines on the other hand, such asphenol/formaldehyde resins, urea/formaldehyde resins andmelamine/formaldehyde resins.

21. Drying and non-drying alkyd resins.

22. Unsaturated polyester resins which are derived from copolyesters ofsaturated and unsaturated dicarboxylic acids with polyhydric alcoholsand vinyl compounds as crosslinking agents, and also halogen-containingmodifications thereof of low flammability.

23. Thermosetting acrylic resins, derived from substituted acrylicesters, such as epoxy-acrylates, urethane-acrylates or polyesteracrylates.

24. Alkyd resins, polyester resins or acrylate resins in admixture withmelamine resins, urea resins, polyisocyanates or epoxide resins ascrosslinking agents.

25. Crosslinked epoxide resins which are derived from polyepoxides, forexample from bis-glycidyl ethers or from cycloaliphatic diepoxides.

26. Natural polymers, such as cellulose, rubber, gelatin and derivativesthereof which are chemically modified in a polymer homologous manner,such as cellulose acetates, cellulose propionates and cellulosebutyrates, or the cellulose ethers, such as methyl cellulose.

27. Mixtures of polymers as mentioned above, for example PP/EPDM,Polyamide 6/EPDM or ABS, PVC/EVA, PVC/ABS, PVC/MBS, PC/ABS, PBTP/ABS.

28. Naturally occuring and synthetic organic materials which are puremonomeric compounds or mixtures of such compounds, for example mineraloils, animal and vegetable fats, oil and waxes, or oils, fats and waxesbased on synthetic esters (e.g. phthalates, adipates, phosphates ortrimellitates) and also mixtures of synthetic esters with mineral oilsin any weight ratios, which materials may be used as plasticizers forpolymers or as textile spinning oils, as well as aqueous emulsions ofsuch materials.

29. Aqueous emulsions of natural or synthetic rubber, e.g. natural latexor latices of carboxylated styrene/butadiene copolymers.

30. Polysiloxanes such as the soft, hydrophilic polysiloxanes described,for example, in U.S. Pat. No. 4,259,467; and the hardpolyorganosiloxanes described, for example, in U.S. Pat. No. 4,355,147.

31. Polyketimines in combination with unsaturated acrylicpolyacetoacetate resins or with unsaturated acrylic resins. Theunsaturated acrylic resins include the urethane acrylates, polyetheracrylates, vinyl or acryl copolymers with pendant unsaturated groups andthe acrylated melamines. The polyketimines are prepared from polyaminesand ketones in the presence of an acid catalyst.

32. Radiation curable compositions containing ethylenically unsaturatedmonomers or oligomers and a polyunsaturated aliphatic oligomer.

33. Epoxymelamine resins such as light-stable epoxy resins crosslinkedby an epoxy functional coetherified high solids melamine resin such asLSE-4103 (Monsanto).

In general, the compounds of the present invention are employed in fromabout 0.01 to about 5% by weight of the stabilized composition, althoughthis will vary with the particular substrate and application. Anadvantageous range is from about 0.5 to about 2%, and especially 0.1 toabout 1%.

The stabilizers of the instant invention may readily be incorporatedinto the organic polymers by conventional techniques, at any convenientstage prior to the manufacture of shaped articles therefrom. Forexample, the stabilizer may be mixed with the polymer in dry powderform, or a suspension or emulsion of the stabilizer may be mixed with asolution, suspension, or emulsion of the polymer. The resultingstabilized polymer compositions of the invention may optionally alsocontain from about 0.01 to about 5%, preferably from about 0.025 toabout 2%, and especially from about 0.1 to about 1% by weight of variousconventional additives, such as the materials listed below, or mixturesthereof.

1. Antioxidants

1.1. Alkylated monophenols, for example,

2,6-di-tert-butyl-4-methylphenol

2-tert.butyl-4,6-dimethylphenol

2,6-di-tert-butyl-4-ethylphenol

2,6-di-tert-butyl-4-n-butylphenol

2,6-di-tert-butyl-4-i-butylphenol

2,6-di-cyclopentyl-4-methylphenol

2-(α-methylcyclohexyl)-4,6-dimethylphenol

2,6-di-octadecyl-4-methylphenol

2,4,6-tri-cyclohexylphenol

2,6-di-tert-butyl-4-methoxymethylphenol

1.2. Alkylated hydroquinones, for example,

2,6-di-ter-butyl-4-methoxyphenol

2,5-di-tert-butyl-hydroquinone

2,5-di-tert-amyl-hydroquinone

2,6-diphenyl-4-octadecyloxyphenol

1.3. Hydroxylated thiodiphenyl ethers, for example,

2,2'-thio-bis-(6-tert-butyl-4-methylphenol)

2,2'-thio-bis-(4-octylphenol)

4,4'-thio-bis-(6-tert-butyl-3-methylphenol)

4,4'-thio-bis-(6-tert-butyl-2-methylphenol)

1.4. Alkylidene-bisphenols, for example,

2,2'-methylene-bis-(6-tert-butyl-4-methylphenol)

2,2'-methylene-bis-(6-tert-butyl-4-ethylphenol)

2,2'-methylene-bis-[4-methyl-6-(α-methylcyclohexyl)-phenol]

2,2'-methylene-bis-(4-methyl-6-cyclohexylphenol)

2,2'-methylene-bis-(6-nonyl-4-methylphenol)

2,2'-methylene-bis-[6-(α-methylbenzyl)-4-nonylphenol]

2,2'-methylene-bis-[6-(α,α-dimethylbenzyl)-4-nonylphenol]

2,2'-methylene-bis-(4,6-di-tert-butylphenol)

2,2'-ethylidene-bis-(4,6-di-tert-butylphenol)

2,2'-ethylidene-bis-(6-tert-butyl-4-isobutylphenol)

4,4'-methylene-bis-(2,6-di-tert-butylphenol)

4,4'-methylene-bis-(6-tert-butyl-2-methylphenol)

1,1-bis-(5-tert-butyl-4-hydroxy-2-methylphenyl-butane

2,6-di-(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol

1,1,3-tris-(5-tert-butyl-4-hydroxy-2-methylphenyl)-butane

1,1-bis-(5-tert-butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane

ethyleneglycol bis-[3,3-bis-(3'-tert-butyl-4'-hydroxyphenyl)-butyrate]

di-(3-tert-butyl-4-hydroxy-5-methylphenyl)-dicyclopentadiene

di-[2-(3'-tert-butyl-2'-hydroxy-5'-methyl-benzyl)-6-tert-butyl-4-methylphenyl]terephthalate.

1.5. Benzyl compounds, for example,

1,3,5-tri-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene

di-(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide

3,5-di-tert-butyl-4-hydroxybenzyl-mercapto-acetic acid isooctyl ester

bis-(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)dithiol terephthalate

1,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate

1,3,5-tris-(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate

3,5-di-tert-butyl-4-hydroxybenzyl-phosphoric acid dioctadecyl ester

3,5-di-tert-butyl-4-hydroxybenzyl-phosphoric acid monoethyl ester,calcium-salt

1.6. Acylaminophenols, for example,

4-hydroxy-lauric acid anilide

4-hydroxy-stearic acid anilide

2,4-bis-octylmercapto-6-(3,5-tert-butyl-4-hydroxyanilino)-s-triazine

octyl-N-(3,5-di-tert-butyl-4-hydroxyphenyl)-carbamate

1.7. Esters of β-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid withmonohydric or polyhydric alcohols, for example,

    ______________________________________                                        methanol       diethylene glycol                                              octadecanol    triethylene glycol                                             1,6-hexanediol pentaerythritol                                                neopentyl glycol                                                                             tris-hydroxyethyl isocyanurate                                 thiodiethylene glycol                                                                        di-hydroxyethyl oxalic acid diamide                            ______________________________________                                    

1.8. Esters of β-(5-tert-butyl-4-hydroxy-3-methylphenyl)-propionic acidwith monohydric or polyhydric alcohols, for example,

    ______________________________________                                        methanol       diethylene glycol                                              octadecanol    triethylene glycol                                             1,6-hexanediol pentaerythritol                                                neopentyl glycol                                                                             tris-hydroxyethyl isocyanurate                                 thiodiethylene glycol                                                                        di-hydroxyethyl oxalic acid diamide                            ______________________________________                                    

1.9. Amides of β-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid forexample,

N,N'-di-(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)-hexamethylenediamine

N,N'-di-(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)-trimethylenediamine

N,N'-di-(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)-hydrazine

1.10 Diarylamines, for example,

diphenylamine, N-phenyl-1-naphthylamine,N-(4-tert-octylphenyl)-1-naphthylamine,4,4'-di-tert-octyl-diphenylamine, reaction product ofN-phenylbenzylamine and

2,4,4-trimethylpentene, reaction product of diphenylamine and2,4,4-trimethylpentene, reaction product of N-phenyl-1-naphthylamine and2,4,4-trimethylpentene.

2. UV absorbers and light stabilizers

2.1. 2-(2'-Hydroxyphenyl)-benzotriazoles, for example, the 5'-methyl-,3',5'-di-tert-butyl-, 5'-tert-butyl-, 5'-(1,1,3,3-tetramethylbutyl)-,5-chloro-3',5'-di-tert-butyl-, 5-chloro-3'-tert-butyl-5'-methyl-,3'-sec-butyl-5'-tert-butyl-, 4'-octoxy, 3',5'-di-tert-amyl-,3',5'-bis-(α,α-dimethylbenzyl),3'-tert-butyl-5'-(2-(omega-hydroxy-octa-(ethyleneoxy)carbonyl-ethyl)-,3'-dodecyl-5'-methyl-, and 3'-tert-butyl-5'-(2-octyloxycarbonyl)ethyl-,and dodecylated-5'-methyl derivatives.

2.2. 2-Hydroxy-benzophenones, for example, the 4-hydroxy-, 4-methoxy-,4-octoxy, 4-decyloxy-, 4-dodecyloxy-, 4-benzyloxy, 4,2',4'-trihydroxy-and 2'-hydroxy-4,4'-dimethoxy derivatives.

2.3. Esters of optionally substituted benzoic acids for example, phenylsalicylate, 4-tert-butylphenyl salicylate, octylphenyl salicylate,dibenzoylresorcinol, bis-(4-tert-butylbenzoyl)-resorcinol,benzoylresorcinol, 3,5-di-tert-butyl-4-hydroxybenzoic acid2,4-di-tert-butylphenyl ester and 3,5-di-tert-butyl-4-hydroxybenzoicacid hexadecyl ester.

2.4. Acrylates, for example, α-cyano-β,β-diphenylacrylic acid ethylester or isooctyl ester, α-carbomethoxy-cinnamic acid methyl ester,α-cyano-β-methyl-p-methoxy-cinnamic acid methyl ester or butyl ester,α-carbomethoxy-p-methoxy-cinnamic acid methyl ester,N-(β-carbomethoxy-β-cyanovinyl)-2-methyl-indoline.

2.5. Nickel compounds, for example, nickel complexes of2,2'-thio-bis-[4-(1,1,3,3-tetramethylbutyl)-phenol], such as the 1:1 or1:2 complex, optionally with additional ligands such as n-butylamine,triethanolamine or N-cyclohexyl-diethanolamine, nickeldibutyldithiocarbamate, nickel salts of4-hydroxy-3,5-di-tert-butylbenzylphosphonic acid monoalkyl esters, suchas of the methyl, ethyl or butyl ester, nickel complexes of ketoximessuch as of 2-hydroxy-4-methyl-phenyl undecyl ketoxime, nickel complexesof 1-phenyl-4-lauroyl-5-hydroxy-pyrazole, optionally with additionalligands.

2.6. Sterically hindered amines, for examplebis-(2,2,6,6-tetramethylpiperidyl) sebacate,bis-(1,2,2,6,6-pentamethylpiperidyl) sebacate,n-butyl-3,5-di-tert.butyl-4-hydroxybenzyl malonic acidbis-(1,2,2,6,6-pentanemethylpiperidyl)ester, condensation product of1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinicacid, condensation product ofN,N'-(2,2,6,6-tetramethylpiperidyl)-hexamethylenediamine and4-tert-octylamino-2,6-dichloro-s-triazine,tris-(2,2,6,6-tetramethylpiperidyl)-nitrilotriacetate,tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate,1,1'(1,2-ethanediyl)-bis-(3,3,5,5-tetramethylpiperazinone).

2.7. Oxalic acid diamides, for example, 4,4'-di-octyloxy-oxanilide,2,2'-di-octyloxy-5,5'-di-tert-butyl-oxanilide,2,2'-di-dodecyloxy-5,5'-di-tert-butyl-oxanilide,2-ethoxy-2'-ethyl-oxanilide, N,N'-bis(3-dimethylaminopropyl)-oxalamide,2-ethoxy-5-tert-butyl-2'-ethyloxanilide and its mixture with2-ethoxy-2'-ethyl-5,4'-di-tert-butyloxyanilide and mixtures of ortho-and para-methoxy- as well as of o- and p-ethoxy-disubstitutedoxanilides.

2.8. Hydroxyphenyl-s-triazines, for example2,6-bis-(2,4-dimethylphenyl)-4-(2-hydroxy-4-octyloxyphenyl)-s-triazine;2,6-bis-(2,4-dimethylphenyl)-4-(2,4-dihydroxyphenyl)-s-triazine;2,4-bis(2,4-dihydroxyphenyl)-6-(4-chlorophenyl)-s-triazine;2,4-bis[2-hydroxy-4-(2-hydroxyethoxy)phenyl]-6-(4-chlorophenyl)-s-triazine;2,4-bis[2-hydroxy-4-(2-hydroxy-4-(2-hydroxyethoxy)phenyl]-6-(2,4-dimethylphenyl)-s-triazine;2,4-bis[2-hydroxy-4-(2-hydroxyethoxy)phenyl]-6-(4-bromophenyl)-s-triazine;2,4-bis[2-hydroxy-4-(2-acetoxyethoxy)phenyl]-6-(4-chlorophenyl)-s-triazine;2,4-bis(2,4-dihydroxyphenyl)-6-(2,4-dimethylphenyl)-s-triazine.

3. Metal deactivators, for example, N,N'-diphenyloxalic acid diamide,N-salicylal-N'-salicycloylhydrazine, N,N'-bis-salicyloylhydrazine,N,N'-bis-(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazine,3-salicyloylamino-1,2,4-triazole, bis-benzylidene-oxalic aciddihydrazide.

4. Phosphites and phosphonites, for example, triphenyl phosphite,diphenylalkyl phosphites, phenyldialkyl phosphites, tri-(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite,di-stearyl-pentaerythritol diphosphite, tris-(2,4-di-tert-butylphenyl)phosphite, di-isodecylpentaerythritol diphosphite,di-(2,4-di-tert-butylphenyl)pentaerythritol diphosphite,tristearylsorbitol triphosphite, tetrakis-(2,4-di-tert-butylphenyl)4,4'-diphenylylenediphosphonite.

5. Compounds which destroy peroxide, for example, esters ofβ-thiodipropionic acid, for example the lauryl, stearyl, myristyl ortridecyl esters, mercapto-benzimidazole or the zinc salt of2-mercaptobenzimidazole, zinc dibutyl-dithiocarbamate, dioctadecyldisulfide, pentaerythritol tetrakis-(β-dodecylmercapto)-propionate.

6. Hydroxylamines, for example, N,N-dibenzylhydroxylamine,N,N-diethylhydroxylamine, N,N-dioctylhydroxylamine,N,N-dilaurylhydroxylamine, N,N-ditetradecylhydroxylamine,N,N-dihexadecylhydroxylamine, N,N-dioctadecylhydroxylamine,N-hexadecyl-N-octadecylhydroxylamine,N-heptadecyl-N-octadecylhydroxylamine, N,N-dialkylhydroxylamine derivedfrom hydrogenated tallow amine.

7. Nitrones, for example, N-benzyl-alpha-phenyl nitrone,N-ethyl-alpha-methyl nitrone, N-octyl-alpha-heptyl nitrone,N-lauryl-alpha-undecyl nitrone, N-tetradecyl-alpha-tridecyl nitrone,N-hexadecyl-alpha-pentadecyl nitrone,N-octadecyl-alpha-heptadecylnitrone, N-hexadecyl-alpha-heptadecylnitrone, N-octadecyl-alpha-pentadecyl nitrone,N-heptadecyl-alpha-heptadecyl nitrone, N-octadecyl-alpha-hexadecylnitrone, nitrone derived from N,N-dialkylhydroxylamine derived fromhydrogenated tallow amine.

8. Polyamide stabilizers, for example copper salts in combination withiodides and/or phosphorus compounds and salts of divalent manganese.

9. Basic co-stabilizers, for example, melamine, polyvinylpyrrolidone,dicyandiamide, triallyl cyanurate, urea derivatives, hydrazinederivatives, amines, polyamides, polyurethanes, alkali metal salts andalkaline earth metal salts of higher fatty acids for example Castearate, Zn stearate, Mg stearate, Na ricinoleate and K palmitate,antimony pyrocatecholate or zinc pyrocatecholate.

10. Nucleating agents, for example, 4-tert-butyl-benzoic acid, adipicacid, diphenylacetic acid.

11. Fillers and reinforcing agents, for example, calcium carbonate,silicates, glass fibers, asbestos, talc, kaolin, mica, barium sulfate,metal oxides and hydroxides, carbon black, graphite.

12. Other additives, for example, plasticizers, lubricants, emulsifiers,pigments, optical brighteners, flameproofing agents, anti-static agents,blowing agents and thiosynergists such as dilauryl thiodipropionate ordistearyl thiodipropionate.

The phenolic antioxidant of particular interest is selected from thegroup consisting of n-octadecyl3,5-di-tert-butyl-4-hydroxyhydrocinnamate, neopentanetetrayltetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinammate), di-n-octadecyl3,5-di-tert-butyl-4-hydroxybenzylphosphonate,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate,thiodiethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnammate),1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene,3,6-dioxaoctamethylenebis(3-methyl-5-tert-butyl-4-hydroxyhydrocinnamate),2,6-di-tert-butyl-p-cresol,2,2'-ethylidene-bis(4,6-di-tert-butylphenol),1,3,5-tris(2,6-dimethyl-4-tert-butyl-3-hydroxybenzyl)isocynurate,1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane,1,3,5-tris[2-(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyloxy)ethyl]isocyanurate,3,5-di-(3,5-di-tert-butyl-4-hydroxybenzyl)mesitol, hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate),1-(3,5-di-tert-butyl-4-hydroxyanilino)-3,5-di(octylthio)-s-triazine,N,N'-hexamethylene-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamide),calcium bis(ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate),ethylene bis[3,3-di(3-tert-butyl-4-hydroxyphenyl)butyrate], octyl3,5-di-tert-butyl-4-hydroxybenzylmercaptoacetate,bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide, andN,N'-bis[2-(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyloxy)-ethyl]-oxamide.

A most preferred phenolic antioxidant is neopentanetetrayltetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), n-octadecyl3,5-di-tert-butyl-4-hydroxyhydrocinnamate,1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate,2,6-di-tert-butyl-p-cresol or2,2'-ethylidene-bis(4,6-di-tert-butylphenol).

The hindered amine compound of particular interest is selected from thegroup consisting of

bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate,

bis(1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate,

di(1,2,2,6,6-pentamethylpiperidin-4-yl)(3,5-di-tert-butyl-4-hydroxybenzyl)butylmalonate,

4-benzoyl-2,2,6,6-tetramethylpiperidine,4-stearyloxy-2,2,6,6-tetramethylpiperidine,

3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triaza-spiro[4.5]decane-2,4-dione,

tris(2,2,6,6-tetramethylpiperidin-4-yl) nitrilotriacetate,

1,2-bis(2,2,6,6-tetramethyl-3-oxopiperazin-4-yl)ethane,2,2,4,4-tetramethyl-7-oxa-3,20-diaza-21-oxodispiro[5.1.11.2]heneicosane,polycondensation product of 2,4-dichloro-6-tert-octylamino-s-triazineand 4,4'-hexamethylenebis(amino-2,2,6,6-tetramethylpiperidine),

polycondensation product of1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinicacid, polycondensation product of4,4'-hexamethylenebis-(amino-2,2,6,6-tetramethylpiperidine) and1,2-dibromoethane,

tetrakis(2,2,6,6-tetramethylpiperidin-4-yl)1,2,3,4-butanetetracarboxylate,

tetrakis(1,2,2,6,6-pentamethylpiperidin-4-yl)1,2,3,4-butanetetracarboxylate,

polycondensation product of 2,4-dichloro-6-morpholino-s-triazine and

4,4'-hexamethylenebis(amino-2,2,6,6-tetramethylpiperidine),N,N',N",N"'-tetrakis[(4,6-bis(butyl-2,2,6,6-tetramethyl-piperidin-4-yl)-amino-s-triazin-2-yl]-1,10-diamino-4,7-diazadecane,

mixed[2,2,6,6-tetramethylpiperidin-4-yl/β,β,β',β'-tetramethyl-3,9-(2,4,8,10-tetraoxaspiro[5.5]undecane)diethyl]1,2,3,4-butanetetracarboxylate,

mixed[1,2,2,6,6-pentamethylpiperidin-4-yl/β,β,β',β'-tetramethyl-3,9-(2,4,8,10-tetraoxaspiro[5.5]undecane)diethyl]1,2,3,4-butanetetracarboxylate,octamethylene bis(2,2,6,6-tetramethylpiperidin-4-carboxylate) and

4,4'-ethylenebis(2,2,6,6-tetramethylpiperazin-3-one).

A most preferred hindered amine compound isbis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate, the polycondensationproduct of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperdine andsuccinic acid, the polycondensation product of2,4-dichloro-6-tert-octylamino-s-triazine and4,4'-hexamethylenebis(amino-2,2,6,6-tetramethylpiperidine) orN,N',N",N"'-tetrakis[(4,6-bis(butyl-(2,2,6,6-tetramethyl-piperidin-4-yl)amino)-s-triazine-2-yl]-1,10-diamino-4,7-diazadecane.

The following examples are presented for the purpose of illustrationonly and are not to be construed to limit the nature of scope of theinstant invention in any manner whatsoever.

EXAMPLE 1 Di-tert-butyl Ketoxime

The title compound is prepared according to the procedure of G. D.Mendenhall and K. U. Ingold, J. Amer. Chem. Soc., 95, 2963 (1973).

EXAMPLE 2 2-Cyano-2-methyleicosane

To a solution of 24 mL of a 2.5M n-butyllithium solution in hexanes and60 mL of tetrahydrofuran at -78° C. is added dropwise 6.07 g ofdiisopropylamine. After the reaction mixture is stirred at thistemperature for 15 minutes, a solution of 5.5 mL of isobutyronitrile in60 mL of tetrahydrofuran is added dropwise and the resultant reactionmixture is stirred for 2 hours at -78° C. To the reaction mixture atroom temperature is added a solution of 20 g of 1-bromooctadecane in 50mL of tetrahydrofuran. The reaction mixture is stirred for 18 hours atroom temperature and then 100 mL of saturated ammonium chloride isadded. To the reaction mixture is added 100 mL of diethyl ether and theorganic phase is separated. The organic phase is dried over anhydrousmagnesium sulfate and the solvent is removed in vacuo to give 18.2 g ofthe title compound as a white solid. The ¹ H NMR spectrum is consistentwith the desired product.

EXAMPLE 3 Tert-butyl 2-Methyleicosan-2-yl Ketooxime

To a suspension of 2-cyano-2-methyleicosane in 30 mL of pentane cooledwith a water bath is added dropwise 17.6 mL of a 1.7M tert-butyllithiumsolution in pentane. The reaction mixture is heated at reflux for 1hour. To the reaction mixture is added sequentially 3 mL of ethanol, 2mL of acetic acid, and 2.12 g of hydroxylamine hydrochloride and theresultant reaction mixture is stirred for 18 hours at room temperature.The precipitate is removed by filtration and the collected solids arerecrystallized from hexane to give 6.1 g (51.4%) of the title compoundas a white solid melting at 92°-94° C.

Analysis: Calcd. for C₂₆ H₅₃ NO: C, 78.9; H, 13.5; N, 3.5. Found: C,79.2; H, 13.7; N, 3.4.

EXAMPLE 4 2,9-Dicyano-2,9-dimethyldecane

By the procedure used to prepare the compound of Example 2, the titlecompound is prepared from 24 mL of a 2.5M n-butyllithium solution inhexanes, 6.07 g of diisopropylamine, 5.5 mL of isobutyronitrile, 7.32 gof 1,6-dibromohexane, and 120 mL of tetrahydrofuran. The IR and ¹ H NMRspectra of the white solid (7.7 g) obtained were consistent withstructure of the desired product.

EXAMPLE 5 2,2,4,4,11,11,13,13-Octamethyl-3,12-dioximinotetradecane

By the procedure used to prepare the compound of Example 3, the titlecompound is prepared from 7.7 g of 2,9-dicyano-2,9-dimethyldecane, 35.3mL of a 1.7M tert-butyllithium solution in pentane, 30 mL of pentane, 6mL of ethanol, 4 mL of acetic acid, and 4.24 g of hydroxylaminehydrochloride. The residue is purified by trituration sequentially withmethanol and hot ethanol to give 4.9 g (44%) of the title compound as awhite solid melting at 203°-209° C.

Analysis: Calcd. for C₂₂ H₄₄ N₂ O₂ : C, 71.7; H, 12.0; N, 7.6. Found: C,71.8; H, 11.8; N, 7.4.

EXAMPLE 6 Tert-butyl 3,4-Dimethoxyphenyl Ketooxime

By the procedure used to prepare the compound of Example 3, the titlecompound is prepared from 10.0 g of 3,4-dimethoxybenzonitrile, 36 mL ofa 1.7M tert-butyllithium solution in pentane, 30 mL of pentane, 6 mL ofethanol, 4 mL of acetic acid, and 4.24 g of hydroxylamine hydrochloride.The residue was purified by recrystallization from methanol to give 2.1g (15%) of the title compound as a white solid melting at 203°-209° C.

Analysis: Calcd. for C₁₃ H₁₉ NO: C, 65.8; H, 8.1; N, 5.9. Found: C,65.7; H, 8.2; N, 5.9.

EXAMPLE 7 Process Stabilization of Polypropylene at 536° F. (280° C.)

This example illustrates the thermal stabilizing effectiveness of theinstant compounds in new technology polypropylene.

The base formulation comprises unstabilized new technology polypropylene(PROFAX 6501, HIMONT) containing 0.1% by weight of calcium stearate. Thetest stabilizer is dry blended, if a solid, or solvent blended, if aliquid, onto polypropylene from a solution in methylene chloride. Afterremoval of the solvent by evaporation under reduced pressure, thestabilized resin formulation is extruded at 80 rpm from a 1 inch (2.54cm) diameter extruded at 536° F. (280° C.). The residence time in theextruder is 45 seconds.

After each of the first and fifth extrusions, the melt flow rate (ingrams/10 minutes) is measured according to ASTM method D-1238 on thepellets obtained. The closer the melt flow rate after the fifthextrusion is to the melt flow rate after the first extrusion the lesspolymer degradation has occurred. Close values would indicate superiorprocess stabilization efficacy bestowed by the test stabilizer.

The test results are shown in the table below.

    ______________________________________                                                Additive      Melt Flow Rate                                                  Concentration After Extrusion                                         Additive* (% by weight)   1      5                                            ______________________________________                                        None      --              10.7   30                                           AO A      0.1             4.3    12.7                                         Example 1 0.1             3.5    15.6                                         Example 3 0.1             4.1    18.1                                         Example 5 0.1             3.2    17.2                                         ______________________________________                                         *AO A is neopentanetetrayl                                                    tetrakis(3,5di-tert-butyl-4-hydroxyhydrocinnamate).                      

These data show that the sterically hindered oximes provide improvedmelt flow values compared to the control. After one extrusion the meltflow values are similar to that provided by a phenolic antioxidant.

EXAMPLE 8 Color Stabilization of Polypropylene Processed at 536° F.(280° C.)C

When polypropylene is extruded as described in Example 7, resin pelletsobtained after the first and fifth extrusions are compression moldedinto 125 mil (3.2 mm) thick plaques at 380° F. (193° C.) and specimenyellowness index (YI) values are determined according to ASTM methodD-1925. Low YI values indicate less yellowing and discoloration.

The results are given in the table below.

    ______________________________________                                                             Yellowness Index                                                 Additive     Value After                                                      Concentration                                                                              Extrusion                                                Additive* (% by weight)  1        5                                           ______________________________________                                        None      --             2.2      3.3                                         AO A      0.1            8.4      10.5                                        Example 1 0.1            0.2      3.4                                         Example 3 0.1            0.6      3.2                                         Example 5 0.1            0.5      5.7                                         ______________________________________                                         *AO A is neopentanetetrayl                                                    tetrakis(3,5di-tert-butyl-4-hydroxyhydrocinnamate).                      

Improved resistance to discoloration as measured by yellowness indexvalues is observed when the instant sterically hindered oximes are usedcompared to conventional hindered phenolic antioxidants. Surprisingly,the YI color after one extrusion is superior to that of the base resinitself when the hindered oximes are employed.

EXAMPLE 9 Process Stabilization of Polypropylene at 536° F. (280° C.)

Following the procedure set forth in Example 7, a combination of instantsterically hindered oxime plus a phenolic antioxidant are used tostabilize the polypropylene. The melt flow rates after the first andfifth extrusions are measured to assess the effectiveness of thiscombination of stabilizers.

The test results are shown in the table below.

    ______________________________________                                                Additive      Melt Flow Rate                                                  Concentration After Extrusion                                         Additive* (% by weight)   1      5                                            ______________________________________                                        None      --              10.7   30                                           AO A      0.1             4.3    12.7                                         AO A plus 0.1             3.5    12.1                                         Example 1  0.05                                                               AO A plus 0.1             4.4    14.8                                         Example 3  0.05                                                               AO A plus 0.1             4.0    18.1                                         Example 5  0.05                                                               ______________________________________                                         *AO A is neopentanetetrayl                                                    tetrakis(3,5ditert-butyl-4-hydroxyhydrocinnamate).                       

These data show that the sterically hindered oximes in combination withhindered phenolic anitoxidants provide improved melt flow valuescompared to the control.

EXAMPLE 10 Color Stabilization of Polypropylene Processed at 536° F.(280° C.)

Following the procedure set forth in Example 7, a combination of instantsterically hindered oxime plus a phenolic antioxidant are used tostabilize the polypropylene. The resin pellets obtained after the firstand fifth extrusions are compression molded into 125 mil (3.2 mm) thickplaques at 380° F. (193° C.) and specimen yellowness index (YI) valuesare determined according to ASTM method D-1925. Low YI values indicateless yellowing and discoloration.

The results are given in the table below.

    ______________________________________                                                             Yellowness Index                                                 Additive     Value After                                                      Concentration                                                                              Extrusion                                                Additive* (% by weight)  1        5                                           ______________________________________                                        None      --             2.2      3.3                                         AO A      0.1            8.4      10.5                                        AO A plus 0.1            5.2      8.0                                         Example 1  0.05                                                               AO A plus 0.1            7.4      7.6                                         Example 3  0.05                                                               AO A plus 0.1            5.0      7.6                                         Example 5  0.05                                                               ______________________________________                                         *AO A is neopentanetetrayl                                                    tetrakis(3,5di-tert-butyl-4-hydroxyhydrocinnamate).                      

Improved resistance to discoloration as measured by yellowness indexvalues is observed when the instant sterically hindered oximes are usedin combination with a conventional hindered phenolic antioxidant. Thecombination of phenolic antioxidant plus sterically hindered oximeprovides better resistance to discoloration than use of the phenolicantioxidant alone.

What is claimed is:
 1. A polyolefin composition stabilized againstdiscoloration during processing at elevated temperature which consistsessentially of(a) polyethylene or polypropylene, and (b) an effectivestabilizing amount of a compound of formula I ##STR2## wherein R₁ is atert-alkyl group of 4 to 18 carbon atoms, aryl of 6 to 10 carbon atomsor said aryl substituted by one or two alkyl of 1 to 4 carbon atoms orby one or two alkoxy of 1 to 4 carbon atoms,R₂ and R₃ are independentlyalkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms,phenylalkyl of 7 to 9 carbon atoms, aryl of 6 to 10 carbon atoms, orsaid aryl or said phenylalkyl substituted on the phenyl ring by one ortwo alkyl of 1 to 4 carbon atoms or by one or two alkoxy of 1 to 4carbon atoms; or R₂ and R₃ together are a straight or branched chainalkylene of 4 to 10 carbon atoms, n is an integer from 1 to 4, when n is1, T is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbonatoms, phenylalkyl of 7 to 9 carbon atoms, aryl of 6 to 10 carbon atoms,or said aryl or said phenylalkyl substituted on the phenyl ring by oneor two alkyl of 1 to 4 carbon atoms or by one or two alkoxy of 1 to 4carbon atoms, when n is 2, T is alkylene of 2 to 12 carbon atoms,xylylene, arylene of 6 to 10 carbon atoms or said arylene substituted byone or two alkyl of 1 to 4 carbon atoms or by one or two alkoxy of 1 to4 carbon atoms, and when n is 3 or 4, T is alkanetriyl of 3 to 10 carbonatoms, or alkanetetrayl of 4 to 10 carbon atoms.
 2. A compositionaccording to claim 1 wherein the polyolefin is polypropylene.
 3. Acomposition according to claim 1 where in the compound of formula I, R₁is tert-alkyl of 4 to 8 carbon atoms, phenyl or phenyl substituted byone or two alkyl of 1 to 2 carbon atoms or by one or two alkoxy of 1 to2 carbon atoms.
 4. A composition according to claim 3 wherein R₁ istert-butyl, phenyl or phenyl substituted by one or two methyl or by oneor two methoxy.
 5. A composition according to claim 1 where in thecompound of formula I, R₂ and R₃ are independently alkyl of 1 to 8carbon atoms.
 6. A composition according to claim 5 wherein R₂ and R₃are methyl.
 7. A composition according to claim 1 where in the compoundof formula I, n is 1 or
 2. 8. A composition according to claim 1 wherein the compound of formula I, when n is 1, T is alkyl of 8 to 18 carbonatoms or benzyl.
 9. A composition according to claim 8 wherein T isalkyl of 12 to 18 carbon atoms.
 10. A composition according to claim 9wherein T is n-octadecyl.
 11. A composition according to claim 1 wherein the compound of formula I, when n is 2, T is alkylene of 2 to 10carbon atoms.
 12. A composition according to claim 11 wherein T isalkylene of 4 to 8 carbon atoms.
 13. A composition according to claim 12wherein T is hexamethylene.
 14. A composition according to claim 1wherein the compound of formula I is di-tert-butyl ketoxime; tert-butyl2-methyleicosan-2-yl ketooxime;2,2,4,4,11,11,13,13-octamethyl-3,12-dioximinotetradecane; or tert-butyl3,4-dimethoxyphenyl ketooxime.